By setting a placeholder sample_type and then writing real data into
raw_data, we mimic the direct sample method to write data at the end.
Note that some data serve only as placeholders and will be overwritten
by the data in raw_data. Additionally, since the IP will be updated in
evsel__parse_sample(), there is no need to handle it in off_cpu_write().
Suggested-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Howard Chu <howardchu95@gmail.com>
---
tools/perf/util/bpf_off_cpu.c | 116 +++++++++++++++++++++-------------
1 file changed, 72 insertions(+), 44 deletions(-)
diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
index f7233a09ec77..2a1cfd7e0b09 100644
--- a/tools/perf/util/bpf_off_cpu.c
+++ b/tools/perf/util/bpf_off_cpu.c
@@ -138,12 +138,19 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
int ncpus = 1, ntasks = 1, ncgrps = 1;
struct strlist *pid_slist = NULL;
struct str_node *pos;
+ struct evsel *evsel;
if (off_cpu_config(evlist) < 0) {
pr_err("Failed to config off-cpu BPF event\n");
return -1;
}
+ evsel = evlist__find_evsel_by_str(evlist, OFFCPU_EVENT);
+ if (evsel == NULL) {
+ pr_err("%s evsel not found\n", OFFCPU_EVENT);
+ return -1 ;
+ }
+
skel = off_cpu_bpf__open();
if (!skel) {
pr_err("Failed to open off-cpu BPF skeleton\n");
@@ -259,7 +266,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
}
if (evlist__first(evlist)->cgrp) {
- struct evsel *evsel;
u8 val = 1;
fd = bpf_map__fd(skel->maps.cgroup_filter);
@@ -280,6 +286,7 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
}
}
+ skel->bss->sample_type = OFFCPU_EMBEDDED_SAMPLE_TYPES;
skel->bss->offcpu_thresh = opts->off_cpu_thresh * 1000;
err = off_cpu_bpf__attach(skel);
@@ -305,7 +312,8 @@ int off_cpu_write(struct perf_session *session)
{
int bytes = 0, size;
int fd, stack;
- u64 sample_type, val, sid = 0;
+ u32 raw_size;
+ u64 sample_type_off_cpu, sample_type_bpf_output, val, sid = 0, tstamp = OFF_CPU_TIMESTAMP;
struct evsel *evsel;
struct perf_data_file *file = &session->data->file;
struct off_cpu_key prev, key;
@@ -315,7 +323,6 @@ int off_cpu_write(struct perf_session *session)
.misc = PERF_RECORD_MISC_USER,
},
};
- u64 tstamp = OFF_CPU_TIMESTAMP;
skel->bss->enabled = 0;
@@ -325,15 +332,10 @@ int off_cpu_write(struct perf_session *session)
return 0;
}
- sample_type = evsel->core.attr.sample_type;
-
- if (sample_type & ~OFFCPU_SAMPLE_TYPES) {
- pr_err("not supported sample type: %llx\n",
- (unsigned long long)sample_type);
- return -1;
- }
+ sample_type_off_cpu = OFFCPU_EMBEDDED_SAMPLE_TYPES;
+ sample_type_bpf_output = evsel->core.attr.sample_type;
- if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER)) {
+ if (sample_type_bpf_output & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER)) {
if (evsel->core.id)
sid = evsel->core.id[0];
}
@@ -344,49 +346,75 @@ int off_cpu_write(struct perf_session *session)
while (!bpf_map_get_next_key(fd, &prev, &key)) {
int n = 1; /* start from perf_event_header */
- int ip_pos = -1;
+ int i = 0; /* raw data index */
bpf_map_lookup_elem(fd, &key, &val);
- if (sample_type & PERF_SAMPLE_IDENTIFIER)
+ /*
+ * Zero-fill some of these fields first, they will be overwritten by the dummy
+ * embedded data (in raw_data) below, when parsing the samples. And because embedded
+ * data is in BPF output, perf script -F without bpf-output field will not work
+ * properly.
+ */
+ if (sample_type_bpf_output & PERF_SAMPLE_IDENTIFIER)
data.array[n++] = sid;
- if (sample_type & PERF_SAMPLE_IP) {
- ip_pos = n;
- data.array[n++] = 0; /* will be updated */
- }
- if (sample_type & PERF_SAMPLE_TID)
- data.array[n++] = (u64)key.pid << 32 | key.tgid;
- if (sample_type & PERF_SAMPLE_TIME)
- data.array[n++] = tstamp;
- if (sample_type & PERF_SAMPLE_ID)
- data.array[n++] = sid;
- if (sample_type & PERF_SAMPLE_CPU)
+ if (sample_type_bpf_output & PERF_SAMPLE_IP)
data.array[n++] = 0;
- if (sample_type & PERF_SAMPLE_PERIOD)
- data.array[n++] = val;
- if (sample_type & PERF_SAMPLE_CALLCHAIN) {
- int len = 0;
-
- /* data.array[n] is callchain->nr (updated later) */
- data.array[n + 1] = PERF_CONTEXT_USER;
- data.array[n + 2] = 0;
+ if (sample_type_bpf_output & PERF_SAMPLE_TID)
+ data.array[n++] = 0;
+ if (sample_type_bpf_output & PERF_SAMPLE_TIME)
+ data.array[n++] = tstamp; /* we won't overwrite time */
+ if (sample_type_bpf_output & PERF_SAMPLE_CPU)
+ data.array[n++] = 0;
+ if (sample_type_bpf_output & PERF_SAMPLE_PERIOD)
+ data.array[n++] = 0;
+ if (sample_type_bpf_output & PERF_SAMPLE_RAW) {
+ /*
+ * the format of raw data is as follows:
+ *
+ * [ size ][ data ]
+ * [ data ]
+ * [ data ]
+ * [ data ]
+ * [ data ][ empty]
+ *
+ */
+ if (sample_type_off_cpu & PERF_SAMPLE_TID)
+ off_cpu_raw_data[i++] = (u64)key.pid << 32 | key.tgid;
+ if (sample_type_off_cpu & PERF_SAMPLE_PERIOD)
+ off_cpu_raw_data[i++] = val;
+ if (sample_type_off_cpu & PERF_SAMPLE_CALLCHAIN) {
+ int len = 0;
+
+ /* off_cpu_raw_data[n] is callchain->nr (updated later) */
+ off_cpu_raw_data[i + 1] = PERF_CONTEXT_USER;
+ off_cpu_raw_data[i + 2] = 0;
+
+ bpf_map_lookup_elem(stack, &key.stack_id, &off_cpu_raw_data[i + 2]);
+ while (off_cpu_raw_data[i + 2 + len])
+ len++;
+
+ /* update length of callchain */
+ off_cpu_raw_data[i] = len + 1;
+
+ /* calculate sample callchain off_cpu_raw_data length */
+ i += len + 2;
+ }
+ if (sample_type_off_cpu & PERF_SAMPLE_CGROUP)
+ off_cpu_raw_data[i++] = key.cgroup_id;
- bpf_map_lookup_elem(stack, &key.stack_id, &data.array[n + 2]);
- while (data.array[n + 2 + len])
- len++;
+ raw_size = i * sizeof(u64) + sizeof(u32); /* 4 empty bytes for alignment */
- /* update length of callchain */
- data.array[n] = len + 1;
+ /* raw_size */
+ memcpy((void *)data.array + n * sizeof(u64), &raw_size, sizeof(raw_size));
- /* update sample ip with the first callchain entry */
- if (ip_pos >= 0)
- data.array[ip_pos] = data.array[n + 2];
+ /* raw_data */
+ memcpy((void *)data.array + n * sizeof(u64) + sizeof(u32), off_cpu_raw_data, i * sizeof(u64));
- /* calculate sample callchain data array length */
- n += len + 2;
+ n += i + 1;
}
- if (sample_type & PERF_SAMPLE_CGROUP)
- data.array[n++] = key.cgroup_id;
+ if (sample_type_bpf_output & PERF_SAMPLE_CGROUP)
+ data.array[n++] = 0;
size = n * sizeof(u64);
data.hdr.size = size;
--
2.43.0On Fri, Sep 27, 2024 at 01:27:33PM -0700, Howard Chu wrote:
> By setting a placeholder sample_type and then writing real data into
> raw_data, we mimic the direct sample method to write data at the end.
>
> Note that some data serve only as placeholders and will be overwritten
> by the data in raw_data. Additionally, since the IP will be updated in
> evsel__parse_sample(), there is no need to handle it in off_cpu_write().
>
> Suggested-by: Namhyung Kim <namhyung@kernel.org>
> Signed-off-by: Howard Chu <howardchu95@gmail.com>
> ---
> tools/perf/util/bpf_off_cpu.c | 116 +++++++++++++++++++++-------------
> 1 file changed, 72 insertions(+), 44 deletions(-)
>
> diff --git a/tools/perf/util/bpf_off_cpu.c b/tools/perf/util/bpf_off_cpu.c
> index f7233a09ec77..2a1cfd7e0b09 100644
> --- a/tools/perf/util/bpf_off_cpu.c
> +++ b/tools/perf/util/bpf_off_cpu.c
> @@ -138,12 +138,19 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
> int ncpus = 1, ntasks = 1, ncgrps = 1;
> struct strlist *pid_slist = NULL;
> struct str_node *pos;
> + struct evsel *evsel;
>
> if (off_cpu_config(evlist) < 0) {
> pr_err("Failed to config off-cpu BPF event\n");
> return -1;
> }
>
> + evsel = evlist__find_evsel_by_str(evlist, OFFCPU_EVENT);
> + if (evsel == NULL) {
> + pr_err("%s evsel not found\n", OFFCPU_EVENT);
> + return -1 ;
> + }
> +
> skel = off_cpu_bpf__open();
> if (!skel) {
> pr_err("Failed to open off-cpu BPF skeleton\n");
> @@ -259,7 +266,6 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
> }
>
> if (evlist__first(evlist)->cgrp) {
> - struct evsel *evsel;
> u8 val = 1;
>
> fd = bpf_map__fd(skel->maps.cgroup_filter);
> @@ -280,6 +286,7 @@ int off_cpu_prepare(struct evlist *evlist, struct target *target,
> }
> }
>
> + skel->bss->sample_type = OFFCPU_EMBEDDED_SAMPLE_TYPES;
Hmm.. you set the sample_type unconditionally which means the embedded
data in the raw area has the fixed format. Then I think you don't need
the sample_type variable at all.
> skel->bss->offcpu_thresh = opts->off_cpu_thresh * 1000;
>
> err = off_cpu_bpf__attach(skel);
> @@ -305,7 +312,8 @@ int off_cpu_write(struct perf_session *session)
> {
> int bytes = 0, size;
> int fd, stack;
> - u64 sample_type, val, sid = 0;
> + u32 raw_size;
> + u64 sample_type_off_cpu, sample_type_bpf_output, val, sid = 0, tstamp = OFF_CPU_TIMESTAMP;
> struct evsel *evsel;
> struct perf_data_file *file = &session->data->file;
> struct off_cpu_key prev, key;
> @@ -315,7 +323,6 @@ int off_cpu_write(struct perf_session *session)
> .misc = PERF_RECORD_MISC_USER,
> },
> };
> - u64 tstamp = OFF_CPU_TIMESTAMP;
>
> skel->bss->enabled = 0;
>
> @@ -325,15 +332,10 @@ int off_cpu_write(struct perf_session *session)
> return 0;
> }
>
> - sample_type = evsel->core.attr.sample_type;
> -
> - if (sample_type & ~OFFCPU_SAMPLE_TYPES) {
> - pr_err("not supported sample type: %llx\n",
> - (unsigned long long)sample_type);
> - return -1;
> - }
> + sample_type_off_cpu = OFFCPU_EMBEDDED_SAMPLE_TYPES;
> + sample_type_bpf_output = evsel->core.attr.sample_type;
>
> - if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER)) {
> + if (sample_type_bpf_output & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER)) {
> if (evsel->core.id)
> sid = evsel->core.id[0];
> }
> @@ -344,49 +346,75 @@ int off_cpu_write(struct perf_session *session)
>
> while (!bpf_map_get_next_key(fd, &prev, &key)) {
> int n = 1; /* start from perf_event_header */
> - int ip_pos = -1;
> + int i = 0; /* raw data index */
>
> bpf_map_lookup_elem(fd, &key, &val);
>
> - if (sample_type & PERF_SAMPLE_IDENTIFIER)
> + /*
> + * Zero-fill some of these fields first, they will be overwritten by the dummy
> + * embedded data (in raw_data) below, when parsing the samples. And because embedded
> + * data is in BPF output, perf script -F without bpf-output field will not work
> + * properly.
> + */
> + if (sample_type_bpf_output & PERF_SAMPLE_IDENTIFIER)
> data.array[n++] = sid;
> - if (sample_type & PERF_SAMPLE_IP) {
> - ip_pos = n;
> - data.array[n++] = 0; /* will be updated */
> - }
> - if (sample_type & PERF_SAMPLE_TID)
> - data.array[n++] = (u64)key.pid << 32 | key.tgid;
> - if (sample_type & PERF_SAMPLE_TIME)
> - data.array[n++] = tstamp;
> - if (sample_type & PERF_SAMPLE_ID)
> - data.array[n++] = sid;
> - if (sample_type & PERF_SAMPLE_CPU)
> + if (sample_type_bpf_output & PERF_SAMPLE_IP)
> data.array[n++] = 0;
> - if (sample_type & PERF_SAMPLE_PERIOD)
> - data.array[n++] = val;
> - if (sample_type & PERF_SAMPLE_CALLCHAIN) {
> - int len = 0;
> -
> - /* data.array[n] is callchain->nr (updated later) */
> - data.array[n + 1] = PERF_CONTEXT_USER;
> - data.array[n + 2] = 0;
> + if (sample_type_bpf_output & PERF_SAMPLE_TID)
> + data.array[n++] = 0;
I'm not sure if it works correctly. You haven't set the callchain
length and 'n' is not updated.
> + if (sample_type_bpf_output & PERF_SAMPLE_TIME)
> + data.array[n++] = tstamp; /* we won't overwrite time */
> + if (sample_type_bpf_output & PERF_SAMPLE_CPU)
> + data.array[n++] = 0;
> + if (sample_type_bpf_output & PERF_SAMPLE_PERIOD)
> + data.array[n++] = 0;
> + if (sample_type_bpf_output & PERF_SAMPLE_RAW) {
> + /*
> + * the format of raw data is as follows:
> + *
> + * [ size ][ data ]
> + * [ data ]
> + * [ data ]
> + * [ data ]
> + * [ data ][ empty]
> + *
> + */
> + if (sample_type_off_cpu & PERF_SAMPLE_TID)
As I said, you can get rid of the sample_type_off_cpu check if it's
always true.
Thanks,
Namhyung
> + off_cpu_raw_data[i++] = (u64)key.pid << 32 | key.tgid;
> + if (sample_type_off_cpu & PERF_SAMPLE_PERIOD)
> + off_cpu_raw_data[i++] = val;
> + if (sample_type_off_cpu & PERF_SAMPLE_CALLCHAIN) {
> + int len = 0;
> +
> + /* off_cpu_raw_data[n] is callchain->nr (updated later) */
> + off_cpu_raw_data[i + 1] = PERF_CONTEXT_USER;
> + off_cpu_raw_data[i + 2] = 0;
> +
> + bpf_map_lookup_elem(stack, &key.stack_id, &off_cpu_raw_data[i + 2]);
> + while (off_cpu_raw_data[i + 2 + len])
> + len++;
> +
> + /* update length of callchain */
> + off_cpu_raw_data[i] = len + 1;
> +
> + /* calculate sample callchain off_cpu_raw_data length */
> + i += len + 2;
> + }
> + if (sample_type_off_cpu & PERF_SAMPLE_CGROUP)
> + off_cpu_raw_data[i++] = key.cgroup_id;
>
> - bpf_map_lookup_elem(stack, &key.stack_id, &data.array[n + 2]);
> - while (data.array[n + 2 + len])
> - len++;
> + raw_size = i * sizeof(u64) + sizeof(u32); /* 4 empty bytes for alignment */
>
> - /* update length of callchain */
> - data.array[n] = len + 1;
> + /* raw_size */
> + memcpy((void *)data.array + n * sizeof(u64), &raw_size, sizeof(raw_size));
>
> - /* update sample ip with the first callchain entry */
> - if (ip_pos >= 0)
> - data.array[ip_pos] = data.array[n + 2];
> + /* raw_data */
> + memcpy((void *)data.array + n * sizeof(u64) + sizeof(u32), off_cpu_raw_data, i * sizeof(u64));
>
> - /* calculate sample callchain data array length */
> - n += len + 2;
> + n += i + 1;
> }
> - if (sample_type & PERF_SAMPLE_CGROUP)
> - data.array[n++] = key.cgroup_id;
> + if (sample_type_bpf_output & PERF_SAMPLE_CGROUP)
> + data.array[n++] = 0;
>
> size = n * sizeof(u64);
> data.hdr.size = size;
> --
> 2.43.0
>
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